// Programming_Scala/src/ch12/mutable-type-variance-script.scala
// WON'T COMPILE:  Mutable parameterized types can't have variance annotations

class ContainerPlus[ +A ]( var value: A )      // ERROR
class ContainerMinus[ -A ]( var value: A )     // ERROR

println( new ContainerPlus( "Hello, World!" ) )
println( new ContainerMinus( "Hello, World!" ) )
